Erected in 1961 to stop the mass exodus of East Germans to the West, the Berlin Wall is a grim symbol of the Cold War. Wyden describes superpower confrontations in which the Wall has been central, and reveals in detail the policies and punishments imposed on citizens who either try to cross it or merely express a desire to live in the West. The story of Ota and Barbel Grubel is typical: the couple was imprisoned and forced to give up their children for adoption after an escape attempt in 1973. Among the successful escapes we read of here is the dramatic 1979 flight in a hot-air balloon by the Gunther Wetzel family. Wyden ( The Passionate War ) concludes that reunification of the two countries is unlikely in the foreseeable future, given the magnitude of the ideological and cultural chasm separating them and the disparity in national value systems. That disparity is forcefully elucidated in these pages, and makes very clear why thousands of East Germans are taking advantage of the recent opening of the border between Hungary and Austria. Photos. BOMC selection. (Nov.)